What is Quantum Supremacy, claimed by Google?

On Wednesday Oct 23,2019 Google announced that it has achieved a breakthrough called quantum supremacy in computing.

Scientists have developed an experimental processor that took just 200 seconds, to complete a calculation that would have taken a classical computer 10,000 years.

What is quantum computing?

It derives from quantum mechanics, which deals with the behaviour of particles at the scale of atoms and subatomic particles. At that tiny scale, many rules of classical physics cease to apply, and the unique rules of quantum physics come into play.
A quantum computer will seek to operate on the same principles of quantum mechanics. Developing such a computer has been the goal of scientists since the 1980s. By simulating the behaviour of atoms and particles, a quantum computer would perform extremely complicated tasks that are beyond the scope of classical computers, or would take an incredibly short time to perform tasks that would have taken years of work from a classical computer, as in this case.

What makes a quantum computer so powerful?

The work came from Google’s research lab in the University of Santa Barbara, California. In their research paper published in the journal Nature, scientists have announced that their Sycamore computer has solved a problem that is considered intractable for classical computers. This was achieved by developing an architecture of what are known as “qubits”

“Qubits” is short for “quantum bits”, which are to quantum computers what bits are to traditional computers. Each bit holds information in the form of one of two values — either 1 or 0 — which can be connected into various combinations. On the other hand, a qubit can be both 0 and 1 at the same time. The more the number of qubits, the higher the amount of information, which increases exponentially compared to the information stored in the same number of bits.

What exactly has Google achieved?

From the development of a single superconducting qubit, the researchers proceeded to systems including an architecture of 54 qubits with Sycamore. One of these did not perform, the University of California, Santa Barbara said in a statement. This architecture led to the 53 qubits being entangled into a superposition state. Preparing this superposition state was accomplished in a matter of microseconds. The researchers then sampled from this distribution by measuring the qubits a million times in 200 seconds. The equivalent task for a state-of-the-art classical supercomputer would take approximately 10,000 years, they wrote in their paper.